The present invention relates to recovery of the wash product generated when cleaning discharge chutes and other concrete dispensing equipment, and more particularly to wash product containment and recycling devices installed or retrofit to transit concrete mixers.
Major concrete installations typically employ transit concrete mixing vehicles, also known as concrete mixers or trucks, to deliver loads of concrete from a concrete production facility to the construction site. The trucks have rotating drums that mix the concrete during transit, so that the concrete is thoroughly mixed and ready for dispensing when the truck reaches the site. After dispensing, a concrete residue remains on the discharge chutes, hoppers, and tools such as shovels and trowels used to handle, guide, and shape the concrete. To prevent the residue from hardening, these components are cleaned on site, typically by rinsing them with water. The resulting residue of this cleaning, i.e. concrete wash product, includes water, dissolved cementatious materials, suspended fine particulates, and larger aggregate. The water is highly alkaline due to the dissolved materials, and consequently is considered a potential groundwater contaminant. Thus, the previous practice of simply dumping concrete wash product onto the ground at the construction site is generally prohibited by local ordinance, state statutes, or regulations.
A variety of systems and devices have been proposed to address the heightened environmental concern. For example, U.S. Pat. No. 7,117,995 (Connard, III), U.S. Pat. No. 7,147,360 (Elefsrud), and U.S. Patent Application Publication No, 2006/0000490 (Barragan et al.) disclose concrete mixing trucks equipped with containers for collecting the concrete wash product generated as discharge chutes and other components are rinsed.
Several of the systems involve returning the residue to the mixing drum. In U.S. Pat. No. 6,155,277 (Barry) and U.S. Pat. No. 6,866,047 (Marvin), a pump is used to transfer collected concrete wash product back into the drum. U.S. Pat. No. 6,039,468 (Kowalcyzk) shows a system in which a washout bucket mounted on a catwalk during transit is placed under the discharge chute during cleaning. After cleaning, the bucket is removably mounted to the booster axle frame, to be lifted by the frame to dump its contents into the mixing drum. In U.S. Pat. No. 5,741,065 (Bell et al.), a canister is placed below the discharge chute during cleaning. After cleaning, the canister is attached to an upright rail mounted to the mixing truck, then lifted upwardly along the rail until the canister is tilted to empty its contents into the drum.
Although these approaches are useful for avoiding groundwater contamination, they raise problems which to date have not been satisfactorily addressed. The removably mounted containers are difficult to maneuver due to their bulk and weight, especially when filled with concrete wash product. They are inconvenient, due to the need to attach and later detach the container from the rail, the booster axle frame, or other mechanism used to lift the container to a height sufficient for emptying its contents into the mixing drum. Time is required to remove the container from the fixture that supports it during transit from the concrete plant to the construction site, and further time is lost reattaching the container to the fixture after returning its contents to the mixing drum.
Some systems attempt to counteract these problems by permanently mounting the container to the mixing truck chassis. These systems rely on pumps or air pressure to lift the concrete wash product from the container into the drum, and neither approach is particularly reliable in cold weather. The alternative is to haul the collected concrete wash product back to the concrete plant for disposal or other handling.
Systems that recover concrete wash product and return it to the mixing drum advantageously reduce the risk of groundwater contamination while facilitating reuse of a product that otherwise goes to waste. However, if the content of the mixing drum is not taken into account at the concrete plant when the constituents of the next batch are loaded into the drum, there is a risk of unintentional and undesirable alteration of constituent ratios.
Therefore, the present invention has several aspects directed to one or more of the following objects:                to provide a container for collecting concrete wash product, mounted to a transit concrete mixer through a mechanism suitable for supporting the container in transit operable to alternatively lower the container for collecting concrete wash product and raise the container for returning collected wash product to the mixing drum;        to provide a device for mounting a container to a booster axle frame of a transit concrete mixer such that the usual pivoting of the booster axle frame moves the container between a wash product collecting position and a wash product dispensing position;        to provide a process for the recovery of concrete wash product by gravity, and the return of collected wash product by gravity to a mixing drum of a transit concrete mixer for reuse, without manually lifting, mounting, dismounting, or otherwise handling the container used for such recovery and return; and        to provide a device for measuring concrete wash product collected in a container while cleaning the discharge chute and other concrete dispensing components.        